Affiliation
CNR Istituto Nanoscienze, NEST Lab, Pisa
Talk Title
Designing helical superconductivity in Al/NiBr2 thin films
Abstract
Magnetism and superconductivity, two antagonist orders in bulk materials, can coexist at the nanoscale and generate exotic states with novel functionalities at the base of superconducting spintronics1 . Seminal works from the 80’s have demonstrated this strong hybridization in thin bilayers of ferromagnetic insulators and conventional superconductors such as EuS and Al2,3 with appealing applications for quasiparticle diodes4 and heat engines5. A step-forward in designing unconventional superconductors can be made by replacing the uniformly magnetized EuS with a magnetic layer of helical order for the implementation of a helical superconductor.
Here I show the realization of such a helical superconductivity in Al/NiBr2 thin films. This exotic state of matter is quantified by measuring the magnetochiral supercurrent diode effect observed upon the application of an in-plane magnetic field. The vectorial symmetries of the effect with a maximal rectification for fields orthogonal to the current direction reveal the conical spin pattern expected in the NiBr2 surface6 . The hybridization of such bilayer makes it a promising platform for designing exotic states and future quantum electronics on conventional superconductors like Al proximized by NiBr2 Van der Waals material.
1 J. Linder, and J.W.A. Robinson, “Superconducting spintronics,” Nat Phys 11(4), 307–315 (2015).
2 P.M. Tedrow, J.E. Tkaczyk, and A. Kumar, “Spin-Polarized Electron Tunneling Study of an Artificially Layered Superconductor with Internal Magnetic Field: EuO-Al,” Phys. Rev. Lett. 56(16), 1746–1749 (1986).
3 E. Strambini, V.N. Golovach, G. De Simoni, J.S. Moodera, F.S. Bergeret, and F. Giazotto, “Revealing the magnetic proximity effect in EuS/Al bilayers through superconducting tunneling spectroscopy,” Phys. Rev. Materials 1(5), 054402 (2017).
4 E. Strambini, M. Spies, N. Ligato, S. Ilić, M. Rouco, C. González-Orellana, M. Ilyn, C. Rogero, F.S. Bergeret, J.S. Moodera, P. Virtanen, T.T. Heikkilä, and F. Giazotto, “Superconducting spintronic tunnel diode,” Nat Commun 13(1), 2431 (2022).
5 C.I.L. de Araujo, P. Virtanen, M. Spies, C. González-Orellana, S. Kerschbaumer, M. Ilyn, C. Rogero, T.T. Heikkilä, F. Giazotto, and E. Strambini, “Superconducting Spintronic Heat Engine,” (2023).
6 D. Amoroso, P. Barone, and S. Picozzi, “Spontaneous skyrmionic lattice from anisotropic symmetric exchange in a Ni-halide monolayer,” Nat Commun 11(1), 5784 (2020).
ACKNOWLEDGMENT: This project has received funding from the European Union’s HORIZON-EIC- 2021-TRANSITIONOPEN-01 -SPECTRUM - G.A.101057977